<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        *{
            margin: 0;
            padding: 0;
        }
        .box{
            width: 600px;
            height: 600px;
            background-color: pink;
            /* 
                grid布局是一种网格布局
            */
            display: grid;
            grid-template-columns: repeat(3,100px);
            grid-template-rows: repeat(3,100px);
        }
        .item{
            background-color: skyblue;
            border: 1px solid aqua;
        }
        .item:nth-child(3){
            /* 
                grid-column-start:2 ;左边所在的垂直网格线
                grid-column-end: 3;右边框所在的垂直网格线
                grid-row-start: 1;上边框所在的水平网格线
                grid-row-end: 2;下边框所在的水平网格线
                如果有重叠 z-index调整显示层级
            */
            grid-column-start:3;
            grid-column-end: 4;
            grid-row-start: 3;
            grid-row-end: 4;
            z-index: 3;
        }
        .item:nth-child(4){
            background-color: blue;
            grid-column-start:3;
            grid-column-end: 4;
            grid-row-start: 3;
            grid-row-end: 4;
        }
    </style>
</head>
<body>
    <div class="box">
        <div class="item">1</div>
        <div class="item">2</div>
        <div class="item">3</div>
        <div class="item">4</div>
        <div class="item">5</div>
        <div class="item">6</div>
        <div class="item">7</div>
        <div class="item">8</div>
        <div class="item">9</div>
    </div>
</body>
</html>